Trends, not absolutes
Wrist-based trackers are best understood as trend monitors, not precision instruments. Your step count, sleep stages, and resting heart rate are estimates with real margins of error. The value is in the direction they move over weeks and months, not any single day's number.
Chasing an exact step target down to the digit misses the point. What matters is whether you are consistently more active this month than last month.
The metrics worth watching
Resting heart rate is one of the more useful signals, because a declining trend over months often reflects improving cardiovascular fitness. Sleep duration is worth tracking simply because most people underestimate how little they sleep. Steps are useful as a broad gauge of daily movement.
Calorie burn estimates are the least reliable number on any tracker. They vary so much between devices and individuals that they are best ignored for anything beyond entertainment.
The habit is the point
The best feature of a fitness tracker is not the sensor — it is the reminder to move. A device that nudges you to walk, stand, and notice your sleep is worth more than any metric it produces. Choose a tracker you will actually wear, and let the numbers serve the habit rather than the other way around.